Field of the Invention
The present invention relates to an air diffusion device for efficiently supplying air and other gases in a process that requires dissolved oxygen, and more particularly, to an improved air diffusion device capable of ensuring easy assembly and enhanced aeration efficiency.
Description of the Related Art
Due to continuous industrialization and urbanization, environmental contamination is worsening and kinds of wastewater, dirty water, and sewage are also diversified. Facilities for treatment thereof are being advanced and treatment cost is increasing.
Currently, biological treatment methods, which are selectively combined with physical and chemical methods, are mainly used for wastewater treatment. These biological treatment methods may basically be classified into two kinds, i.e. an aerotropic treatment method and an anaerobic treatment method.
Anaerobic treatment advantageously does not require the supply of oxygen and achieves the acquisition of combustible methane gas as an energy source, but has disadvantages, such as long reaction duration, generation of bad odor, and the like. Most wastewater treatment facilities employ aerotropic treatment owing to advantages, such as short reaction duration, perfect removal of organic materials, and the like, although aerotropic treatment disadvantageously requires energy consumption for the supply of oxygen, for example.
In aerotropic treatment, the supply of oxygen is essential to the growth and activity of aerotropic microorganisms. To this end, an air diffusion device is used. The air diffusion device is installed in an aeration tank (reactor), and serves to maintain an appropriate amount of Dissolved Oxygen (DO) in the aeration tank. Gas is dispersed in wastewater in the aeration tank, and therefore a bubble size, bubble hold-up, contact between gas and liquid, and flow characteristics of gas and liquid have a great effect on operational conditions, performance, efficiency, and the like of the aeration tank.
An efficient method for increasing a contact area between gas and liquid in an aeration tank and increasing a mass transfer coefficient between gas and liquid is to increase bubble hold-up. To this end, uniform generation of bubbles having a reduced size is essential. During rising, bubbles are increased in size while coalesced in the aeration tank. This is because a bubble rising velocity increases in proportion to a bubble size, and therefore increase in the size of bubbles reduces a bubble hold-up period. In a case in which bubbles have a large size and generation of bubbles is not uniform, the bubbles will have a short hold-up period in the aeration tank, which causes deterioration of Standard Oxygen Transfer Efficiency (SOTE).
Various shapes of air diffusion devices, such as a pipe-shaped air diffusion device, a ball-shaped air diffusion device, a disc-shaped air diffusion device, and the like, have been developed and used. In addition, a multistage disc-shaped air diffusion device, in which a plurality of discs is arranged in multiple stages to increase the supply amount of air, has been supposed.